How Often Do Women Need a Bone Density Test?

Women with normal bones may delay retesting

Women over 65 with normal results on a bone density test to detect osteoporosis may not need to be retested every other year and possibly can wait considerably longer than that, according to new research.

The study, published in the New England Journal of Medicine and funded by the National Institutes of Health, attempts to clarify how often a woman should have a test so her doctor can catch the condition in its early stages and start treatment before she breaks a bone.

Should You Have a Bone Density Test Before Age 65?

Some women may not need routine bone density screenings every two years. — Photo by Untitled X-Ray/Getty Images

Professional groups agree that younger women should also be screened if they have risk factors that increase the chances of a fracture. These include:

A baseline bone density test is recommended by the National Osteoporosis Foundation and other professional groups for all women 65 years old and older. Medicare pays for a test every two years and many doctors order them that frequently.

But the U.S. Preventive Services Task Force, an independent panel that evaluates evidence for health services, has argued that there is no strong scientific evidence to support routine testing every two years.

The researchers sought to shed light on the debate by analyzing data from nearly 5,000 women 67 years old and older who were part of a long-running nationwide research study that began in 1986. None of the women had osteoporosis or a history of hip or spinal fractures at the start of the study. They all had bone density measurements early in the study and periodically thereafter, starting two years later.

The researchers sorted the women into four groups, according to their T-scores, a measure that compares bone density to that of a healthy 30-year-old. They then determined how often they would have had to be screened before 10 percent of them developed osteoporosis.

Decoding Your T-Score

The gold-standard test for bone density is a DXA, which provides precise measurement of bone density with minimal radiation. The lower your score, the greater the risk of a fracture.

According to the National Institutes of Health:

A T-score between 1 and -1 is normal and healthy. If you fall within this range, you typically don't need treatment for osteoporosis.

A T-score between -1 and -2.5 indicates mild bone loss.

A T-score of -2.5 or lower indicates osteoporosis. The greater the negative number, the more severe the bone loss.

The World Health Organization’s FRAX tool can help calculate whether treatment is needed for low bone density.

The researchers found that high-risk women with advanced bone thinning needed the most frequent screening, because it took only a year for 10 percent of them to progress to osteoporosis. Women with moderate bone loss were found to benefit from a test after five years. Surprisingly, it took more than 15 years for 10 percent of the women with normal bone density or mild bone loss to develop osteoporosis — longer than the researchers expected.

Based on the study results, women without risk factors should “ask for a bone density test as soon as possible after age 65” and then discuss the appropriate time for the next test with their doctor, says lead author Margaret Gourlay, M.D., of the University of North Carolina at Chapel Hill. “That would be much more effective than relying on imaging specialists to dictate screening schedules.”

Clifford Rosen, M.D., of Tufts University School of Medicine in Boston, who was not involved in the study, agrees that more flexible guidelines are needed. “Let's target women who need more frequent tests, rather than putting all women on a regular schedule, whether they need a scan or not.”